This invention relates to streak tubes, and more particularly to a trigger circuit for a streak tube.
A streak camera requires an ultra high speed ramp voltage generating circuit in which, upon application of a trigger signal, the voltage is changed about 2000 volts in several nanoseconds. In this case, pulse light applied to the photoemitting surface of the streak tube is partly reflected to be applied to a pin photodiode to thereby generate a trigger signal, and this trigger signal is used to start a switching circuit of avalanche transistors to thereby provide the above-described high speed ramp voltage. The ramp voltage is applied to the deflecting plates of the streak tube to deflect the flow of electrons emitted from the photoemitting surface, whereby the relation between time and incident optical intensity is observed as the relation between position and luminescent intensity on the phosphor screen.
If the duration of the above-mentioned light pulse is in the range of picoseconds, as in a mode locked Nd: glass laser, the intensity of the light pulse will vary within about .+-.50%. When an avalanche transistor is driven by an output signal of a pin photodiode which receives such a light pulse, the delay time which elapses from the application of the trigger signal to the avalanche transistor until the switching circuit of the avalanche transistor is started is not constant, resulting in approximately a one nanosecond difference therebetween. Therefore, it is impossible to define the relation between time and position on the phosphor screen, which prevents accurate measurements.